Migrate documentation to readthedocs

[Neyri]

Migrate the documentation from Github Pages to readthedocs.

• Make sur to keep the pydata template.
• See how we can keep several versions.
• Write a github action to do so

[Neyri]

Several sources of inspiration: https://stackoverflow.com/questions/34020699/how-do-i-override-a-template-on-readthedocs https://docs.readthedocs.io/en/stable/tutorial/#versioning-documentation